The present invention relates to air treatment systems and, more particularly, to a xe2x80x9csmartxe2x80x9d air cleaning system such as for volatile organic compounds and carbon monoxide that may exist in a variety of environments.
There is substantial public and government concern over contaminated air in commercial and residential buildings because of the impact on health and safety, odors, and comfort. This is especially true of modern xe2x80x9ctightxe2x80x9d buildings where the outside ventilation rates are low to reduce air-conditioning and heating costs, and also in locations where the outdoor air itself is contaminated. Most air treatment technologies remove particulates, but do not reduce odorous or harmful gaseous contaminants, like volatile organic compounds (VOCs), carbon monoxide (CO), or ozone (O3). Those that do address these additional contaminants produce significant disadvantages. Adsorbent filters require frequent replacement, have high-pressure drops, and have difficulty removing the lighter of the VOCs, CO, and O3. Catalytic systems have longer lifetimes, less maintenance, and treat a wider variety of contaminants. However, a drawback has been the energy cost of heating the airflow to reaction temperature on a full-time basis.
U.S. Pat. No. 5,742,516 for Indoor Air Quality And Ventilation Assessment Monitoring Device discloses sensors, the outputs of which control an air handler which governs air flow rates and thus ventilation rate. Fundamentally, the ""516 patent discloses a device which improves air quality by diluting a contaminated air stream with a less contaminated air stream. The ""516 patent device relies on a mixing of external air and internal air using the air handler to control fan speed, dampen settings and filtration depending on detectors which monitor the extent of a selected air contaminant such as carbon monoxide, methane or ozone.
U.S. Pat. No. 5,976,010 for Energy Efficient Air Quality Maintenance System And Method discloses a heating, ventilation and air conditioning system which employs air contaminant sensors and compares their measurements to setpoints or standards. The focus is on the air contaminant CO2 and the air quality improvement is also through dilution with less contaminated air (i.e., less CO2).
U.S. Pat. No. 3,772,851 for Dust Monitoring System And Method discloses the removal of particulates from industrial exhaust. The system compares overall particulate level to a standard and then varies the amount of contaminated flow to treat depending upon the extent of overall contamination sensed.
As can be seen, there is a need for an air cleaning system that eliminates VOCs and other gaseous contaminants, as well as particulates.
The present invention improves air quality by eliminating unwanted VOCs that are of high health and safety concern. In one aspect of the present invention, the energy burden that catalytic oxidation requires is reduced through integration of sensors to measure contaminant concentrations and occupancy, and a control methodology to match treatment efficiency to a specified air quality standard. The controller may be programmed with many algorithms, including prediction of catalyst efficiency, which increases with increasing temperature and decreasing flowrate.
In another aspect of the present invention, the VOC concentration in the treatment space decreases with increasing number of air exchanges through the system; and larger differences between actual VOC concentration and desired concentration require more air treatment. In this way the present invention operates when air treatment is needed and conserves power when air quality is acceptable. Unlike the device of the ""516 patent disclosure, the present invention employs sensor outputs to control an air cleaner. Control of the air cleaner is achieved by monitoring air contaminant concentrations in both the inlet and outlet of the air cleaner, and by knowledge of the air cleaner""s efficiency that, under a given set of conditions, can predict contaminant concentrations in the outlet and enclosed space.
Thus, in yet another aspect of the present invention the air cleaner of the present invention may self-select operating conditions (flow rate and temperature) that achieve the desired air quality or that minimize energy in achieving satisfactory air quality.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawing, description and claims.